Process for preparing aromatic or heteroaromatic sulfur compound

ABSTRACT

PCT No. PCT/JP95/02315 Sec. 371 Date Jul. 24, 1996 Sec. 102(e) Date Jul. 24, 1996 PCT Filed Nov. 13, 1995 PCT Pub. No. WO96/16034 PCT Pub. Date May 30, 1996The present invention provides a process for preparing an aromatic or heteroaromatic thiol represented by the formula (2), the process comprising hydrolyzing an aromatic or heteroaromatic halogenated methyl sulfide represented by the formula (1)Ar+545 SCH3-mXm)n(1)Ar+545 SH)n(2)wherein Ar is an aromatic or heteroaromatic ring which has no substituent or which has an optional substituent or substituents, X is a halogen atom, m is an integer of 1 to 3 and n is 1 or 2. According to the present invention, an aromatic or heteroaromatic thiol can be prepared at a commercially low cost and with ease.

This application is a 371 of PCT/JP95/02315 which is now published as WO96/16034 on May 30, 1996.

FIELD OF THE INVENTION

The present invention relates to a novel process for preparing anaromatic or heteroaromatic thiol or an aromatic or heteroaromaticdisulfide and a novel process for preparing an aromatic orheteroaromatic halogenated methyl sulfide which is useful as thestarting material for said thiol or disulfide. The aromatic orheteroaromatic thiol and disulfide are useful compounds which are usedfor various purposes as in pharmaceutical compositions, agriculturalcompositions, functional materials or the like.

BACKGROUND ART

Various processes have been known for preparing an aromatic orheteroaromatic thiol or disulfide. Among them, the conventionalprocesses for preparing an aromatic or heteroaromatic thiol by bondcleavage in alkyl sulfide are classified into the following threeprocesses:

(A) Process comprising reacting an aromatic alkyl sulfide with alkylthiolate in hexamethylphosphoric triamide (abbreviation HMPA) used as asolvent

(Tetrahedron Letters 21 3099 (1980))

(Synthesis Communications 478 (1982)) ##STR1## (B) Process comprisingreacting an aromatic alkyl sulfide with metal sodium in liquid ammonia

(Org. Synth. Coll. Vol.5 419 (1973))

(J. Am. Chem. Soc. 81 4939 (1959)) ##STR2## (C) Process comprisingoxidizing an aromatic methyl sulfide with perbenzoic acid, reacting theoxide with trifluoroacetic acid, and causing triethylamine to act on thereaction mixture

(Tetrahedron Letters 25 1753 (1984)) ##STR3##

However, these conventional processes pose the following drawbacks whencommercially conducted.

The process (A) is defective in that the HMPA used as a solvent is noteasily available and expensive and that the sodium mercaptide used as areagent is difficult to handle in a nonaqueous system. Furtherproblematic is the disposal of dialkyl sulfide produced as a by-product.

The process (B) is industrially difficult to carry out because of highrisks involved in handling, use of an expensive metal sodium andlow-yield production. The process (C) requires a number of reactionprocedures and necessitates the use of an expensive, highly dangerousreaction reagent such as perbenzoic acid, trifluoroacetic acid, etc.

As described above, none of the conventional processes for preparing anaromatic or heteroaromatic thiol by bond cleavage in alkyl sulfide aresatisfactory from the viewpoint of industrial application.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a process for preparingan aromatic or heteroaromatic thiol at a commercially low cost and withease.

Another object of the invention is to provide a process for preparing anaromatic or heteroaromatic disulfide at a commercially low cost and withease.

The present inventors conducted extensive research on the reaction forbond cleavage in alkyl sulfide to overcome the drawbacks of said knownprocesses and to provide processes for preparing aromatic orheteroaromatic thiol and disulfide at commercially low costs and withease.

The inventors' research found that the aromatic or heteroaromatichalogenated methyl sulfide represented by the formula (1) can be easilyhydrolyzed to give the corresponding aromatic or heteroaromatic thiolrepresented by the formula (2) in a high yield. The finding led to thecompletion of the present invention. Stated more specifically, the firstinvention is directed to a process for preparing an aromatic orheteroaromatic thiol represented by the formula (2), the processcomprising hydrolyzing an aromatic or heteroaromatic halogenated methylsulfide represented by the formula (1) as shown below: ##STR4## whereinAr is an aromatic or heteroaromatic ring which has no substituent orwhich has an optional substituent or substituents, X is a halogen atom,m is an integer of 1 to 3 and n is 1 or 2.

Since thiol can be easily converted to disulfide by oxidation, thecorresponding disulfide can be produced by executing an oxidation stepsubsequent to the above-mentioned reaction step. The second invention isdirected to a process for preparing an aromatic or heteroaromaticdisulfide represented by the formula (3), the process comprising thesteps of hydrolyzing an aromatic or heteroaromatic halogenated methylsulfide represented by the formula (1), and oxidizing the reactionmixture as shown below: ##STR5## wherein Ar is an aromatic orheteroaromatic ring which has no substituent or which has an optionalsubstituent or substituents, X is a halogen atom, m is an integer of 1to 3 and n is 1 or 2.

The present invention will be described below in more detail.

The contemplated aromatic or heteroaromatic thiol represented by theformula (2) is prepared in high yields by hydrolyzing an aromatic orheteroaromatic halogenated methyl sulfide represented by the formula(1).

In the formulas, the aromatic or heteroaromatic rings represented by Arare not specifically limited and include a wide variety of aromatic orheteroaromatic rings which have no substituent or which have an optionalsubstituent or substituents. Examples of the aromatic or heteroaromaticring represented by Ar are a benzene ring, naphthalene ring, pyridinering, pyrazole ring, pyrazine ring, triazole ring, oxazole ring,isooxazole ring, thiazole ring, isothiazole ring, thiophene ring,benzothiophene ring, furan ring, benzofuran ring, pyrrole ring, indolering, etc.

Examples of optional substituents are halogen, cyano, formyl, amino,carboxyl or its ester, carbamoyl, alkyl carbonyl, nitro, sulfonic acid,alkyl, alkoxyl, hydroxyl, substituted phenylthio, etc.

Among the aromatic or heteroaromatic rings represented by Ar, preferredare a benzene ring, pyridine ring, thiazole ring, and isothiazole ringwhich have an optional substituent or substituents, and more preferredare benzene rings each having, in an optional position or positions,halogen, cyano, formyl, amino, carboxyl or its ester, carbamoyl, alkylcarbonyl, nitro, sulfonic acid, alkyl, alkoxyl, hydroxyl or substitutedphenylthio.

In the aromatic or heteroaromatic halogenated methyl sulfide representedby the formula (1), X is chlorine, bromine or iodine and m is 1, 2 or 3.Among these substances, chlorine is preferred as X. For hydrolysis tomake smooth progress, desirably m is 2 or 3 or a mixture of sulfideswherein m is 2 or 3 is used.

The hydrolysis takes place and proceeds merely by adding water andheating, thereby producing the desired aromatic or heteroaromatic thiolof the formula (2). The hydrolysis reaction makes smooth progress ifeffected in the presence of an acid. While such acids are notspecifically limited, mineral acids such as hydrochloric acid, sulfuricacid, nitric acid and phosphoric acid are used for economical advantage.Among them, hydrochloric acid and sulfuric acid are more preferred. Theacid is sufficient if its amount is 0.01 to 1 times the weight ofhalogenated methyl sulfide of the formula (1).

In this case, the addition of an alcohol, particularly a lower alcohol,causes the hydrolysis reaction to more smoothly proceed. Examples ofuseful lower alcohols are methanol, ethanol, isopropanol, n-propanol,isobutanol, n-butanol, sec-butanol, etc. Among them, methanol ispreferred from an economical viewpoint. The amount of the alcohol,although not specifically limited, is usually 0.5 to 10 times the weightof halogenated methyl sulfide of the formula (1).

Useful solvents are not specifically limited and even said reactionproceeds without a solvent. Examples of useful solvents are hydrocarbonssuch as hexane, cyclohexane and heptane, halogenated hydrocarbons suchas dichloroethane, dichloromethane and chloroform, aromatic hydrocarbonssuch as benzene, toluene, xylene, chlorobenzene, dichlorobenzene andtrichlorobenzene. The amount of the solvent used is not specificallylimited but is usually 0.1 to 10 times the weight of the halogenatedmethyl sulfide of the formula (1).

The reaction temperature is usually in a range of about 20° to about100° C., preferably about 50° to about 90° C. Too low a reactiontemperature retards the reaction, whereas too high a reactiontemperature causes a side reaction, which results in the decrease ofyields. The reaction time is usually in a range of about 1 to about 10hours.

The aromatic or heteroaromatic thiol produced according to the presentinvention can be isolated by conventional distillation orcrystallization.

The aromatic or heteroaromatic thiols obtainable in the presentinvention include various compounds such as thiophenol,4-chlorothiophenol, 2-chlorothiophenol, 2,4-dichlorothiophenol,2,5-dichlorothiophenol, 3,5-dichlorothiophenol, 2,6-dichlorothiophenol,4-bromothiophenol, 2,4-dibromothiophenol, 1,4-benzenedithiol,1,2-benzenedithiol, 4-butyl-1,2-benzenedithiol, 4-cyanothiophenol,2-cyanothiophenol, 4-methylthiophenol, 2-methylthiophenol,4-hydroxythiophenol, 2-hydroxythiophenol, 4-acetylthiophenol,4-nitrothiophenol, 2-nitrothiophenol, 4-aminothiophenol,2-aminothiophenol, 4-mercaptobenzoic acid, 2-mercaptobenzoic acid,2-formylthiophenol, 4-formylthiophenol, 4-mercaptobenzenesulfonic acid,2-cyano-3-chlorothiophenol, 4-carbamoylthiophenol,4,4'-thiodibenzenethiol, 4,4'-oxydibenzenethiol,4-(phenylthio)benzenethiol, 4-(phenylsulfonyl)benzenethiol,2-pyridinethiol, 4-pyridinethiol, 2-mercaptothiophene,2,6-dimercaptothiophene, 1-naphthalenethiol, 2-naphthalenethiol,2-mercaptopyrazine, 4-mercaptotriazole, 5-mercaptotriazole,2-mercaptooxazole, 4-mercaptooxazole, 4-mercaptoisooxazole,2-mercaptothiazole, 4-mercaptothiazole, and 4-mercaptoisothiazole.

To obtain the aromatic or heteroaromatic disulfide of the formula (3) asthe contemplated product, the object can be easily accomplished byadditionally executing an oxidation step after said hydrolysis reaction.In other words, this can be done by adding an oxidizer after thehydrolysis.

A specific oxidizer is not necessary and conventional known oxidizerscan be used. Oxidation methods employable herein are oxygen oxidation,air oxidation, oxidation involving a halogen such as chlorine, andbromine, oxidation involving a peroxide such as hydrogen peroxide andperacetic acid, and oxidation involving an alkali metal salt ofhypohalous acid such as sodium hypochlorite and sodium hypobromite.

The reaction temperature is variable depending on the oxidation method,and can not be specifically defined. It is usually in a range of about0° to about 100° C., preferably about 30° to about 90° C. Too low areaction temperature results in the reduction of reaction rate, whereastoo high a reaction temperature gives rise to a side reaction, therebylowering the yield. The reaction time is usually in a range of about 0.5to about 15 hours.

The aromatic or heteroaromatic disulfide thus formed can be easilyisolated by crystallization or the like.

The aromatic or heteroaromatic disulfide produced by the presentinvention includes a disulfide derived from said aromatic orheteroaromatic thiol.

As stated above, the aromatic or heteroaromatic thiol represented by theformula (2) can be easily prepared by hydrolyzing the aromatic orheteroaromatic halogenated methyl sulfide represented by the formula(1), and the aromatic or heteroaromatic disulfide represented by theformula (3) can be easily prepared by hydrolyzing the aromatic orheteroaromatic halogenated methyl sulfide represented by the formula(1), followed by oxidation.

The aromatic or heteroaromatic halogenated methyl sulfide of the formula(1) to be used herein can be produced by halogenating the correspondingaromatic or heteroaromatic methyl sulfide represented by the formula (4)(the third invention of the present application). ##STR6## wherein Ar isan aromatic or heteroaromatic ring which has no substituent or which hasan optional substituent or substituents, X is a halogen atom, m is aninteger of 1 to 3 and n is 1 or 2.

When the aromatic or heteroaromatic halogenated methyl sulfide of theformula (1) is prepared by halogenating the aromatic or heteroaromaticmethyl sulfide of the formula (4), chlorine, sulfuryl chloride, bromine,sulfuryl bromide, etc. can be used as a halogenating agent. Among them,chlorine is preferred from an economical viewpoint.

The aromatic or heteroaromatic halogenated methyl sulfide of the formula(1) is a compound wherein m is 1, 2 or 3. If the compound of the formula(1) wherein m is 2 or 3, or a mixture of these compounds is used, thehydrolysis reaction in the subsequent step can proceed smoothly.

The amount of the halogenating agent to be used is 1.5 to 7 moles,preferably 2 to 5 moles, per mole of the aromatic or heteroaromaticmethyl sulfide of the formula (4).

Useful solvents are not specifically limited and even said reactionproceeds without a solvent. Examples of useful solvents are hydrocarbonssuch as hexane, cyclohexane and heptane, halogenated hydrocarbons suchas dichloroethane, dichloromethane and chloroform, and aromatichydrocarbons such as benzene, toluene, xylene, chlorobenzene,dichlorobenzene and trichlorobenzene. The amount of the solvent used isnot specifically limited but is usually 0.1 to 10 times the weight ofaromatic or heteroaromatic methyl sulfide of the formula (4).

The halogenation reaction temperature is usually in a range of about-20° to about 100° C., preferably about -5° to about 60° C., althoughvariable with the contemplated compound. Too low a reaction temperatureretards the reaction, whereas too high a reaction temperature bringsabout a side reaction, which leads to the decrease of the yield.

The aromatic or heteroaromatic halogenated methyl sulfide of the formula(1) thus formed can be isolated by conventional distillation orcrystallization.

To obtain the aromatic or heteroaromatic thiol of the formula (2), orthe aromatic or heteroaromatic disulfide of the formula (3) as thecontemplated product, the reaction mixture of the halogenation reactionitself can be used in the subsequent hydrolysis reaction or oxidationreaction further to hydrolysis reaction without isolation of thearomatic or heteroaromatic halogenated methyl sulfide of the formula(1).

In other words, the present invention provides a process for preparingthe aromatic or heteroaromatic thiol of the formula (2), the processcomprising the steps of halogenating the aromatic or heteroaromaticmethyl sulfide of the formula (4) to give the aromatic or heteroaromatichalogenated methyl sulfide of the formula (1), and hydrolyzing thecompound of the formula (1) (the fourth invention of the presentapplication).

Also the present invention provides a process for preparing the aromaticor heteroaromatic disulfide of the formula (3), the process comprisingthe steps of halogenating the aromatic or heteroaromatic methyl sulfideof the formula (4) to give the aromatic or heteroaromatic halogenatedmethyl sulfide of the formula (1), subsequently hydrolyzing the compoundof the formula (1) and further oxidizing the hydrolyzate (the fifthinvention of the present application).

In these processes, by combining said reactions, the aromatic orheteroaromatic thiol of the formula (2) or the aromatic orheteroaromatic disulfide of the formula (3) is produced from thearomatic or heteroaromatic methyl sulfide of the formula (4) in one potin a high yield.

The present invention provides a novel process for preparing an aromaticor heteroaromatic thiol or disulfide which is used for variousapplications as in pharmaceutical compositions, agriculturalcompositions, functional materials or the like and a novel process forpreparing an aromatic or heteroaromatic halogenated methyl sulfideuseful as the starting material for preparing said thiol or disulfide.According to the processes of the present invention, the end product canbe simply prepared in high yields by halogenating, hydrolyzing andoxidizing a commercially available aromatic or heteroaromatic methylsulfide. Thus the processes of the present invention have pronouncedlyhigh economical and commercial values.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be described below in more detail withreference to Examples to which the present invention is not limited atall.

EXAMPLE 1

A 1-liter, 4-necked flask equipped with a stirrer, thermometer,condenser and gas inlet tube was charged with 227.5 g (1.00 mole) of4-chlorophenyl dichloromethyl sulfide, 50 g of water and 400 g ofmethanol. The mixture was heated to 70° C. for 5 hours to completehydrolysis. After completion of the reaction, water was added toseparate the oil layer. Then distillation gave 136.5 g of4-chlorothiophenol. The yield based on 4-chlorophenyl dichloromethylsulfide was 94.5%.

EXAMPLES 2 to 42

The same procedure as in Example 1 was carried out with exception ofusing the aromatic or heteroaromatic halogenated methyl sulfides listedbelow in Tables 1, 2 and 3 as the starting material in place of thecompound used in Example 1, whereby the corresponding aromatic orheteroaromatic thiols were produced.

                  TABLE 1                                                         ______________________________________                                                                              Yield                                   Ex.  Starting Material Reaction Product                                                                             (%)                                     ______________________________________                                        2    2-Chlorophenyl dichloromethyl                                                                   2-Chlorothiophenol                                                                           93.8                                         sulfide                                                                  3    2-Chlorophenyl trichloromethyl                                                                  2-Chlorothiophenol                                                                           93.5                                         sulfide                                                                  4    2,4-Dichlorophenyl dichloro-                                                                    2,4-Dichlorothiophenol                                                                       94.7                                         methyl sulfide                                                           5    2,5-Dichlorophenyl dichloro-                                                                    2,5-Dichlorothiophenol                                                                       94.6                                         methyl sulfide                                                           6    3,5-Dichlorophenyl dichloro-                                                                    3,5-Dichlorothiophenol                                                                       93.1                                         methyl sulfide                                                           7    2,6-Dichlorophenyl dichloro-                                                                    2,6-Dichlorothiophenol                                                                       95.0                                         methyl sulfide                                                           8    4-Bromophenyl dichloromethyl                                                                    4-Bromothiophenol                                                                            93.3                                         sulfide                                                                  9    4-Bromophenyl trichloromethyl                                                                   4-Bromothiophenol                                                                            94.5                                         sulfide                                                                  10   1,4-Di(dichloromethylthio)                                                                      1,4-Benzenedithiol                                                                           92.5                                         benzene                                                                  11   1,4-Di(trichloromethylthio)                                                                     1,4-Benzenedithiol                                                                           92.2                                         benzene                                                                  12   1,2-Di(dichloromethylthio)                                                                      1,2-Benzenedithiol                                                                           91.4                                         benzene                                                                  13   1,2-Di(dichloromethylthio)-4-                                                                   4-Butyl-1,2-benzene-                                                                         91.8                                         butylbenzene      dithiol                                                14   4-Cyanophenyl dichloromethyl                                                                    4-Cyanothiophenol                                                                            94.5                                         sulfide                                                                  15   2-Cyanophenyl dichloromethyl                                                                    2-Cyanothiophenol                                                                            94.6                                         sulfide                                                                  ______________________________________                                    

                  TABLE 2                                                         ______________________________________                                                                              Yield                                   Ex. Starting Material                                                                              Reaction Product (%)                                     ______________________________________                                        16  2-Cyanophenyl trichloro-                                                                       2-Cyanothiophenol                                                                              95.1                                        methyl sulfide                                                            17  4-Methylphenyl dichloro-                                                                       4-Methylthiophenol                                                                             93.8                                        methyl sulfide                                                            18  4-Hydroxyphenyl dichloro-                                                                      4-Hydroxythiophenol                                                                            94.2                                        methyl sulfide                                                            19  4-Acetylphenyl dichloro-                                                                       4-Acetylthiophenol                                                                             92.4                                        methyl sulfide                                                            20  4-Nitrophenyl dichloro-                                                                        4-Nitrothiophenol                                                                              94.9                                        methyl sulfide                                                            21  2-Aminophenyl dichloro-                                                                        2-Aminothiophenol                                                                              94.2                                        methyl sulfide                                                            22  4-(Dichloromethylthio)                                                                         4-Mercaptobenzoic acid                                                                         93.6                                        benzoic acid                                                              23  4-(Trichloromethylthio)                                                                        4-Mercaptobenzoic acid                                                                         94.2                                        benzoic acid                                                              24  4-Dichloromethylbenzene-                                                                       4-Mercaptobenzenesulfonic                                                                      91.5                                        sulfonic acid    acid                                                     25  2-Cyano-3-chlorophenyl                                                                         2-Cyano-3-chlorothiophenol                                                                     93.5                                        dichloromethyl sulfide                                                    26  4-Carbamoylphenyl dichloro-                                                                    4-Carbamoylthiophenol                                                                          94.1                                        methyl sulfide                                                            27  4,4'-(Dichloromethylthio)                                                                      4,4'-Thiodibenzenethiol                                                                        91.9                                        diphenyl sulfide                                                          28  4,4'-(Trichloromethylthio)                                                                     4,4'-Thiodibenzenethiol                                                                        92.9                                        diphenyl sulfide                                                          29  4,4'-(Dichloromethylthio)                                                                      4,4'-Oxydibenzenethiol                                                                         92.1                                        diphenyl ether                                                            ______________________________________                                    

                  TABLE 3                                                         ______________________________________                                                                              Yield                                   Ex. Starting Material  Reaction Product                                                                             (%)                                     ______________________________________                                        30  4-(Phenylthio)phenyl dichloro-                                                                   4-(Phenylthio)benzene-                                                                       95.2                                        methyl sulfide     thiol                                                  31  4-(Phenylsulfonyl)phenyl dichloro-                                                               4-(Phenylsulfonyl)                                                                           92.9                                        methyl sulfide     benzenethiol                                           32  2-Pyridyl dichloromethyl sulfide                                                                 2-Pyridinethiol                                                                              93.1                                    33  2-Pyridyl trichloromethyl sulfide                                                                2-Pyridinethiol                                                                              94.1                                    34  4-Pyridyl dichloromethyl sulfide                                                                 4-Pyridinethiol                                                                              93.3                                    35  2-Thienyl dichloromethyl sulfide                                                                 2-Mercaptothiophene                                                                          92.1                                    36  1-Naphthyl dichloromethyl sulfide                                                                1-Naphthalenethiol                                                                           94.5                                    37  1-Naphthyl trichloromethyl sulfide                                                               1-Naphthalenethiol                                                                           95.2                                    38  2-Naphthyl dichloromethyl sulfide                                                                2-Naphthalenethiol                                                                           94.8                                    39  2-Pyrazyl dichloromethyl sulfide                                                                 2-Mercaptopyrazine                                                                           93.6                                    40  4-Triazyl dichloromethyl sulfide                                                                 4-Mercaptotriazole                                                                           94.7                                    41  2-Oxazyl dichloromethyl sulfide                                                                  2-Mercaptooxazole                                                                            92.8                                    42  4-Isothiazyl dichloromethyl sulfide                                                              4-Mercaptoisothiazole                                                                        93.1                                    ______________________________________                                    

EXAMPLE 43

A 1-liter, 4-necked flask equipped with a stirrer, thermometer,condenser and gas inlet tube was charged with 227.5 g (1.00 mole) of4-chlorophenyl dichloromethyl sulfide, 50 g of water and 500 g ofmethanol. The mixture was heated to 70° C. for 5 hours to completehydrolysis. After completion of the reaction, 357 g (1.05 moles) of 10%aqueous solution of hydrogen peroxide was added dropwise at 40° C. overa period of 1 hour. The mixture was stirred for 1 hour at the sametemperature. The precipitated crystals were filtered, giving 134.7 g of4,4'-dichlorodiphenyl disulfide in a yield of 93.9% based on4-chlorophenyl dichloromethyl sulfide.

EXAMPLE 44

The same procedure as in Example 43 was carried out with the exceptionof using 2-cyanophenyl dichloromethyl sulfide in place of 4-chlorophenyldichloromethyl sulfide as an aromatic or heteroaromatic halogenatedmethyl sulfide as the starting material, giving 2,2'-dicyanodiphenyldisulfide in a yield of 92.1% based on 2-cyanophenyl dichloromethylsulfide.

EXAMPLE 45

The same procedure as in Example 43 was carried out with the exceptionof using 4-bromophenyl trichloromethyl sulfide in place of4-chlorophenyl dichloromethyl sulfide as an aromatic or heteroaromatichalogenated methyl sulfide as the starting material, giving4,4'-dibromodiphenyl disulfide in a yield of 90.3% based on4-bromophenyl trichloromethyl sulfide.

EXAMPLE 46

A 1-liter, 4-necked flask equipped with a stirrer, thermometer,condenser and dropping funnel was charged with 158.5 g (1.00 mole) of4-chlorothioanisole and 300 g of monochlorobenzene. Chlorine (149.1 g,2.1 moles) was blown into the mixture at 5° C. over 2 hours. Thereafter50 g of water and 500 g of methanol were added, and the mixture washeated at 70° C. for 5 hours to complete hydrolysis. After completion ofthe reaction, water was added to separate the oil layer, andmonochlorobenzene was distilled off. Thereafter, distillation gave 133.3g of 4-chlorothiophenol. The yield based on 4-chlorothioanisole was92.2%.

EXAMPLES 47 to 70

The same procedure as in Example 46 was carried out with exception ofusing the aromatic or heteroaromatic thioanisoles as the startingmaterial listed below in Tables 4 and 5 in place of the compound used inExample 46, whereby the corresponding aromatic or heteroaromatic thiolswere produced.

                  TABLE 4                                                         ______________________________________                                                                             Yield                                    Ex.  Starting Material                                                                              Reaction Product                                                                             (%)                                      ______________________________________                                        47   2-Chlorothioanisole                                                                            2-Chlorothiophenol                                                                           91.5                                     48   2,4-Dichlorothioanisole                                                                        2,4-Dichlorothiophenol                                                                       92.4                                     49   2,5-Dichlorothioanisole                                                                        2,5-Dichlorothiophenol                                                                       92.1                                     50   3,5-Dichlorothioanisole                                                                        3,5-Dichlorothiophenol                                                                       93.0                                     51   2,6-Dichlorothioanisole                                                                        2,6-Dichlorothiophenol                                                                       91.5                                     52   4-Bromothioanisole                                                                             4-Bromothiophenol                                                                            92.5                                     53   1,4-(Dimethylthio)benzene                                                                      1,4-Benzenedithiol                                                                           90.0                                     54   1,2-(Dimethylthio)benzene                                                                      1,2-Benzenedithiol                                                                           89.5                                     55   4-Cyanothioanisole                                                                             4-Cyanothiophenol                                                                            92.5                                     56   2-Cyanothioanisole                                                                             2-Cyanothiophenol                                                                            92.4                                     57   4-Hydroxythioanisole                                                                           4-Hydroxythiophenol                                                                          93.5                                     58   4-Acetylthioanisole                                                                            4-Acetylthiophenol                                                                           90.8                                     59   4-Nitrothioanisole                                                                             4-Nitrothiophenol                                                                            91.5                                     ______________________________________                                    

                  TABLE 5                                                         ______________________________________                                                                              Yield                                   Ex. Starting Material Reaction Product                                                                              (%)                                     ______________________________________                                        60  4-(Methylthio)benzoic acid                                                                      4-Mercaptobenzoic acid                                                                        92.4                                    61  4-Methylthiobenzenesulfonic                                                                     4-Mercaptobenzenesulfonic                                                                     89.2                                        acid              acid                                                    62  4-Carbamoylthioanisole                                                                          4-Carbamoylthiophenol                                                                         89.8                                    63  4,4'-(Dimethylthio)diphenyl                                                                     4,4'-Thiodibenzenethiol                                                                       89.9                                        sulphide                                                                  64  4,4'-(Dimethylthio)diphenyl                                                                     4,4'-Oxydibenzenethiol                                                                        90.4                                        ether                                                                     65  4-(Phenylthio)thioanisole                                                                       4-(Phenylthio)benzenethiol                                                                    91.0                                    66  4-(Phenylsulfonyl)thioanisole                                                                   4-(Phenylsulfonyl)-                                                                           90.5                                                          benzenethiol                                            67  2-Pyridylthioanisole                                                                            2-Pyridinethiol 92.5                                    68  4-Pyridylthioanisole                                                                            4-Pyridinethiol 93.0                                    69  2-Thienylthioanisole                                                                            2-Mercaptothiophene                                                                           92.0                                    70  1-Naphthylthioanisole                                                                           1-Naphthalenethiol                                                                            95.1                                    ______________________________________                                    

EXAMPLE 71

A 1-liter, 4-necked flask equipped with a stirrer, thermometer,condenser and dropping funnel was charged with 158.5 g (1.00 mole) of4-chlorothioanisole and 300 g of monochlorobenzene. Chlorine (149.1 g,2.1 moles) was blown into the mixture at 5° C. over 2 hours. Thereafter50 g of water and 500 g of methanol were added, and the mixture washeated at 70° C. for 5 hours to complete hydrolysis. After completion ofthe reaction, 357 g (1.05 moles) of 10% aqueous solution of hydrogenperoxide was added dropwise at 40° C. over a period of 1 hour. Themixture was stirred for 1 hour at the same temperature. The precipitatedcrystals were filtered, giving 132.0 g of 4,4'-dichlorodiphenyldisulfide in a yield of 92.0% based on 4-chlorothioanisole.

EXAMPLE 72

The same procedure as in Example 71 was carried out with the exceptionof using 2-cyanothioanisole in place of 4-chlorothioanisole as anaromatic or heteroaromatic thioanisole as the starting material, giving2,2'-dicyanodiphenyl disulfide in a yield of 92.1% based on2-cyanothioanisole.

EXAMPLE 73

A 1-liter, 4-necked flask equipped with a stirrer, thermometer,condenser and dropping funnel was charged with 158.5 g (1.00 mole) of4-chlorothioanisole and 300 g of monochlorobenzene. Chlorine (149.1 g,2.1 moles) was blown into the mixture at 5° C. over 2 hours. Thereaction mixture was washed with water and dehydrated with magnesiumsulfate, followed by distilling off monochlorobenzene. Thereafter,distillation gave 220.3 g of 4-chlorophenyl dichloromethyl sulfide in ayield of 96.8% based on 4-chlorothioanisole.

What is claimed is:
 1. A process for preparing an aromatic thiolrepresented by formula (2), said process comprising the step ofhydrolyzing an aromatic halogenated methyl sulfide represented byformula (1):

    Ar--(SCH.sub.3-m X.sub.m).sub.n                            ( 1)

    Ar--(SH).sub.n                                             ( 2)

wherein Ar is an aromatic ring X is a halogen atom, m is an integer of 1to 3, and n is 1 or
 2. 2. The process according to claim 1 wherein X inthe formula (1) is chlorine.
 3. The process according to claim 1 whereinm in the formula (1) is 2 or
 3. 4. The process according to claim 1wherein the hydrolysis is conducted in the presence of an acid.
 5. Theprocess according to claim 4 wherein the acid is hydrochloric acid orsulfuric acid.
 6. The process according to claim 1 wherein thehydrolysis is conducted in the presence of a lower alcohol.
 7. Theprocess according to claim 6 wherein the lower alcohol is methanol. 8.The process according to claim 1, wherein Ar in formulas (1) and (2) isselected from the group consisting of a benzene ring.
 9. The processaccording to claim 8, wherein Ar in formulas (1) and (2) is a benzenering having at least one substituent selected from the group consistingof a halogen, a cyano, formyl, amino, carboxyl group, esterifiedcarboxyl group, carbamoyl, alkyl carbonyl, nitro, sulfonic acid group,alkyl, alkoxyl group, hydroxyl group, and substituted phenylthio group.10. A process for preparing an aromatic disulfide represented by formula(3), said process comprising the steps of hydrolyzing an aromatichalogenated methyl sulfide represented by formula (1), and oxidizing thereaction mixture:

    Ar--(SCH.sub.3-m X.sub.m).sub.n                            ( 1)

    ((HS).sub.n-1 --Ar--S).sub.2 --                            (3)

wherein Ar is an aromatic ring, X is a halogen atom, m is an integer of1 to 3, and n is 1 or
 2. 11. The process according to claim 10 wherein Xin the formula (1) is chlorine.
 12. The process according to claim 10wherein m in the formula (1) is 2 or
 3. 13. The process according toclaim 10 wherein the hydrolysis is conducted in the presence of an acid.14. The process according to claim 13 wherein the acid is hydrochloricacid or sulfuric acid.
 15. The process according to claim 10 wherein thehydrolysis is conducted in the presence of a lower alcohol.
 16. Theprocess according to claim 15 wherein the lower alcohol is methanol. 17.The process according to claim 10, wherein Ar in formulas (1) and (3) isselected from the group consisting of a benzene ring.
 18. The processaccording to claim 17, wherein Ar in formulas (1) and (3) is a benzenering having at least one substituent selected from the group consistingof a halogen, a cyano, formyl, amino, carboxyl group, esterifiedcarboxyl group, carbamoyl, alkyl carbonyl, nitro, sulfonic acid group,alkyl, alkoxyl group, hydroxyl group, and substituted phenylthio group.19. A process for preparing an aromatic halogenated methyl sulfiderepresented by formula (1), said process comprising halogenating anaromatic methyl sulfide represented by formula (4):

    Ar--(SCH.sub.3).sub.n                                      ( 4)

    Ar--(SCH.sub.3-m X.sub.m).sub.n                            ( 1)

wherein Ar is an aromatic ring, X is a halogen atom, m is an integer of1 to 3, and n is 1 or
 2. 20. The process according to claim 19 whereinthe aromatic or heteroaromatic methyl sulfide is halogenated bychlorine.
 21. The process according to claim 19 wherein m in the formula(1) is 2 or
 3. 22. The process according to claim 1, further comprising,prior to the hydrolyzing step, halogenating an aromatic methyl sulfiderepresented by formula (4) to give the aromatic halogenated methylsulfide used in the hydrolyzing step:

    Ar--(SCH.sub.3).sub.n                                      ( 4)

wherein Ar is as defined in formula (1).
 23. The process according toclaim 10, further comprising, prior to the hydrolyzing step,halogenating an aromatic methyl sulfide represented by formula (4) togive the aromatic halogenated methyl sulfide used in the hydrolyzingstep:

    Ar--(SCH.sub.3).sub.n                                      ( 4)

wherein Ar is as defined in formula (1).
 24. The process according toclaim 10, wherein the oxidation is conducted using a hydrogen peroxide.25. The process according to claim 23, wherein the oxidation isconducted using a hydrogen peroxide.